This invention relates to cold-start carburetors, and more particularly to early fuel vaporization heater devices intended to be installed at the carburetor to facilitate the cold starting of an internal combustion engine. Especially the invention relates to PTC type heaters adapted for the above purpose.
In the past various types of fuel pre-heater devices arranged for incorporation at the carburetor or in the fuel system of an automobile have been proposed and produced. These acted on the principle that raising the temperature of the fuel introduced into the cylinders, especially at lower ambient temperatures, facilitated the firing and starting of the engine. Wire wound and other types of resistive heaters were placed in the fuel vapor passages, and found to function well, within the limitations involved.
More recently, with the development of PTC ceramic materials, these were used in various modes in conjunction with carburetors to effect control of the choke valve, control of air by-pass valves and also to impart heat to the fuel and/or fuel air mixture. The advantage of the ceramic PTC heaters was one of self regulation or control of the heating, since the resistance increased and the current decreased greatly as the temperature of the ceramic substance rose, without requiring great dependence on other heat or current regulators. However, the mass of the ceramic being greater than that of wire-type heaters, there was an increased resistance to the flow of the fuel mixture through the carburetor. Also, the ceramic was susceptible of cracking or breakage more easily, and required more care in its handling and fabrication. Moreover, careless installation could result in a cracked ceramic unit and an inoperative device, which then had to be replaced.